An International Search Report for International patent application PCT/US06/22389 was issued on Jan. 29, 2007 The references found included U.S. Pat. No. 4,329,179 of Kutta; published United States patent application 2002/0160151 A1 of Pinault et al., and an article entitled “A Review of Methods for the Manufacture of Residential Roofing Materials (Akibari et al.), dated June 2003. These were reported to be “A” documents, i.e., documents” . . . defining the general state of the art which is not considered to be of particular relevance.”
Roofing shingles are comprised of a headlap portion and a butt portion; granules are often used in both of such portions. Reference may be had, e.g., to U.S. Pat. Nos. 3,921,358 (a composite asphalt-impregnated felt roofing shingle comprising a rectangular sheet having a headlap portion and a butt portion), 4,717,614 (a shingle whose headlap portion is coated with a layer of asphaltic material), 4,900,589 (a process for applying granules to a moving sheet having a headlap area and a butt area for making a shingle roofing product), 6,358,305 (a process of preparing a darkened headlap for a roofing shingle), and the like. The entire disclosure of each of these United States patents is hereby incorporated by reference into this specification.
Many abrasive materials, and many roofing granules (such as headlap granules and prime granules), are made from slag. Processes for making granules from slag are well known. Reference may be had, e.g., to U.S. Pat. Nos. 3,615,329, 4,358,415 (method for producing granules from molten metallurgical slags), 4,374,645 (process for granulation of slag), 4,758,260 (process and device for producing granulated slag sand from blast furnace slag), 4,909,837 (process for granulating molten slag), 6,803,016 (device for atomizing and granulating liquid slags), and the like.
Roofing granules made from coal slag are also well known. Coal slag, and its properties have been widely described in the patent literature. Reference may be had, e.g., to U.S. Pat. Nos. 3,995,079 (artificial turf-like product), 4,174,974 (process for converting coal slag into Portland cement), 4,576,638 (process for the production of ferromanganese), 4,629,506 (process for the production of ferrochromium), 4,971,615 (method and means for producing mineral wool), 5,211,895 (molding process for forming a concrete block) 5,337,824 (coal slag universal fluid), 5,405,648 (coating particulate material with a polymer film), 5,439,056 (coal slag solidification of drilling fluid), 5,681,361 (method of making an abrasive article), 6,001,185 (method for treatment of heavy metal contamination), 6,007,590 (method of making a foraminous abrasive article), 6,109,913 (method for disposing of waste dust), and the like.
Coal slag is also often referred to as “Cyclone Boiler Slag,” “Cyclone Bottom Ash,” “Bottom Ash,” “Slag Residue,” “Black Jack,” etc. Granules made from such coal slag often contain substantial amounts of toxic metals, such as, e.g., arsenic, barium, cadmium, chromium, lead, mercury, selenium, and silver. The concentrations of these metals in a particular matrix may be measured by well known methods such as, e.g., the “Toxicity Characteristic Leaching Procedure” (TCLP), which is described, e.g., in EPA method SW 846-1311.
Heavy metals (such as arsenic, barium, cadmium, chromium, lead, mercury, selenium, and silver) are found to contaminate ground water and, when consumed via drinking water and certain injected foods, they accumulate over time in the human body tissue.
Essential metals are required by all organisms in small quantities in order to accomplish specific catalytic functions. However, at levels exceeding these requirements, both essential and non-essential metals can disturb metabolism by binding non-specifically to biomolecules and by inflicting oxidative damage due to their ability to catalyze redox reactions. This can result in the deactivation of essential enzymatic reactions, damage to cellular structures (especially membranes), and DNA modification (mutagenesis). In humans, exposure to high levels of metals can cause acute toxicity symptoms, while long-term exposure to lower levels can trigger allergies and even cancers. In all organisms, uptake, localization, cytoplasmic concentration, and targeting of micronutrient metals must be tightly controlled in order to meet nutritional needs while avoiding damage. Any non-essential metals that enter organisms by virtue of their chemical similarity to nutrient ions must be detoxified and/or excreted.
Metals tend to accumulate in animals and plants. They enter aquatic organisms through body and respiratory surfaces, and by ingestion of particulate matter and water. Toxicity manifests as impairment of metabolic function, with possible changes to the distribution and abundance of populations. Sublethal effects may include changes in morphology, physiology, biochemistry, behavior and reproduction. Massive fish kills can occur when aluminum and iron are mobilized with drainage from acid sulfate soils. The extent of metal uptake, toxicity and bioaccumulation varies depending on the organism, and can be modified by temperature, pH, turbidity, dissolved oxygen and the concentrations of other metals in solution. Accumulation of metals by aquatic organisms (e.g., bivalves and crabs can be a useful indicator of the presence of metals in biologically available forms. If metal levels in organisms are too high for human consumption, shell-fishing waters are closed.
Coal slag and roofing granules made therefrom, are believed to contain one or more of the aforementioned heavy metals. It is not known to what extent, if any, coal slag particles that are disposed within a biological organism degrade and release either heavy metals and/or other contaminants to the biological organism.
It is known, however, that many products derived from coal, such as coal tar, contain substantial amounts of polycyclic aromatic hydrocarbons (PAH). As is disclosed in an article by D. James Fitzgerald et al., “Application of Benzo(a)pyrene and Coal Tar Tumor Dose—Response Data to a Modified Benchmark Dose Method of Guideline Development,” Environmental Health Perspectives, Volume 112, Number 14, October, 2004, pages 1341-1346, “Polycyclic aromatic hydrocarbons . . . are found at a variety of contaminated sites throughout the world from industries such as coal gasification, coke production . . . and cresoste and asphalt production. Some PAHs, for example the well-studied benzo(a)pyrene . . . , are mutagenic and carcinogenic in experimental animals and probably in humans also . . . .” (See page 1341.)
It is an object of this invention to provide granular materials that can function as roofing granules and that contain less than about 100 parts per million of leachable heavy metals via EPA method SW 846-1311 but that have good adhesion properties when incorporated into a roofing shingle.
It is another object of this invention to provide granular materials that can function well as roofing granules but that do not contain any polycyclic aromatic hydrocarbons and have good adhesion properties when incorporated into a roofing shingle.
It is yet another object of this invention to provide granular materials that, in response to electromagnetic radiation, provides a means for inhibiting the growth of undesirable organisms such as, e.g., algae, bacteria, and mixtures thereof.